System Configuration : I/O Setup : Pro Tools Signal Paths

Pro Tools Signal Paths
For more information, see the following topics:
A signal path is a logical grouping of multiple inputs, outputs, or busses that has a single name and (channel) format. The I/O Setup lets you create, define and name paths according to the configuration of your studio and the needs of each project.
Main Paths and Sub-Paths
Paths in Pro Tools tracks and I/O Setup include main paths and sub-paths.
Main Paths
Main paths are logical groupings of inputs, inserts, busses, or outputs. For example, a master stereo output path will include both its left and right channels.
Sub-Paths
A sub-path represents a signal path within a main path. For example, a default stereo output bus path consists of two mono sub-paths, left and right. Mono tracks and sends can be routed to either mono sub-path of the stereo output bus path.
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It is especially useful to define and name sub-paths for complex mixing setups, such as a 5.1 Surround mix.